Age-related macular degeneration (AMD) is the leading cause of blindness among the elderly in the United States. Choroidal neovascularization (CNV) is largely responsible for severe vision loss from AMD. As new and promising treatments emerge for the treatment of choroidal neovascularization, in vivo approaches will be needed not only to evaluate efficacy, but also to address issues important for clinical trials (e.g., dosing, toxicity). We thereby propose to use an inducible transgenic mouse model as an innovative approach to the study of inhibition of CNV. Specifically, we propose to study the effects of pigment epithelium-derived factor (PEDF), which has emerged as a potent inhibitor of angiogenesis, with dramatic inhibitory effects on corneal, retinal, and choroidal neovascularization. Our long-term oal is to develop PEDF as a ther~eutic modality for the prevention as well as treatment of choroidal neovascularization. We hyaothesize that PEDF can cause regression of existing choroidal neovascularization, in addition to inhibiting CNV formation. Accordingly, we propose the following Specific Aims: (1) Develop a transgenic PEDF mouse model with retina-specific, inducible expression of PEDF. Aim 1 will include the characterization of spatial, temporal, and quantitative expression of induced PEDF in the mouse model. (2) Define the potential of PEDF as a therapeutic agent for choroidal neovascularization using the laser-induced CNV model. Aim 2 will determine if transgenic PEDF expression can prevent choroidal neovascularization as well as cause regression of existing CNV. In addition, Aim 2 will address the PEDF dosage requirements required for prevention of CNV, as well as the duration of PEDF presence necessary for prevention. Finally, Aim 2 will determine if transgenic PEDF expression causes choroidal endothelial cell apoptosis in vivo. In our studies, we will adapt the tetracycline-inducible gene expression system to induce photoreceptor-specific expression of PEDF. We will study the effects of transgenic PEDF expression in mice on laser-induced choroidal neovascularization. It is anticipated that our proposal will provide a strong foundation for further studies regarding the mechanism of PEDF action. In addition, our studies will provide a new experimental approach for the study of candidate inhibitors of CNV, providing important data regarding efficacy, therapeutic dose, frequency of administration, and toxicity.